Quantifying Winning And Losing: The Defensive Version

I thought it might be interesting to do a companion entry to the diary which I posted earlier in the week, and then expand on that analysis a little bit. Using the same 120 Division I football teams as in the previous diary, I started to do similar sorts of the data and did find some intriguing relationships as well as some intriguing quirks in the relationships.

As in the other diary, I first broke down the team averages on some basic dynamics by win total. Below are the results for basic defensive statistics:

Plays

Total Yards

Yards / Play

TDs

Yards / Game

12-13 Wins

935

4387

4.68

28

325.83

11 Wins

920

4614

5.01

33

349.60

10 Wins

945

4915

5.20

37

370.01

9 Wins

935

5197

5.54

42

400.46

8 Wins

917

4962

5.39

41

385.57

7 Wins

914

5056

5.51

44

389.52

6 Wins

924

5257

5.68

45

404.35

5 Wins

891

5027

5.63

48

418.92

4 Wins

849

4910

5.78

46

409.14

3 Wins

858

4985

5.81

50

415.43

2 Wins

874

5326

6.11

52

438.56

0-1 Win

854

5595

6.56

62

466.21

For a point of comparison, the division means for each:

Avg. Yards /Play

Plays

Total Yards

TDs

Avg. Yards / Game

DIVISION I AVERAGE:

5.53

902

4991

43

393.31

The relationship here is roughly linear, but not precisely linear.

Looking at averages for total yards, for example, there are two small dips in the trend – one is at 7 and 8 wins, and the other occurs between 3 and 5 wins. One thing that is intriguing about the 7-8 win range is that there is a preponderance of ACC, Big Ten, Big 12 and Pac-12 teams that sit in this range, most notably Michigan, Wisconsin, Michigan St. (bowl stats included here), as well as Arizona, Oklahoma St., Baylor, Clemson and many others. Indeed, three of the top ten defenses and seven of the top twenty defenses by national ranking (yards / game) sit in this area of the overall chart.

The second anomaly – between 3 and 5 wins - is largely inhabited by teams from lesser discussed conferences, such as the Mountain West, Conference USA, and the bottom tier of teams from the MAC conference. My guess on this one is that it is a quirk of their 2012 schedule and the results of these games, at least when it comes to total yards. In other words, many of these teams seem to be the bottom rung of teams in conferences that don’t have many high-powered offenses. I could be wrong on this, and at some point, I may very break this up into passing vs. rushing to elaborate on this effect.

Next, let’s take a look at top decile and bottom decile performers in the areas of total yards, yards per play, TDs surrendered and average yards per game:

AVG. WINS

AVG. LOSSES

Top 10% Performers - Total Yards

9.2

3.8

Top 10% Performers - Avg. Yards / Play

9.7

3.4

Top 10% Performers - Touchdowns

9.8

3.3

Top 10% Performers - Avg. Yards / Game

9.8

3.3

Bottom 10% Performers - Total Yards

6.7

6.0

Bottom 10% Performers - Avg. Yards / Play

4.0

8.3

Bottom 10% Performers - Touchdowns

4.5

7.9

Bottom 10% Performers - Avg. Yards / Game

4.5

7.8

It seems as if the top decile performances more or less speak for themselves in terms of having a defense that doesn’t give up big plays and can make crucial stops – these elements are, on average, worth about three wins above the division mean. As you may expect, on defense, the bottom decile performances in total yards still harbor the potential to produce decent seasons. Indeed, in this group, you have bowl-eligible teams like UCLA, Baylor, Lousiana Tech and Toledo, so having a defense that surrenders yards in bulk doesn’t mean we won’t see you in December. Of course, that won’t shock anyone, but here’s some statistical confirmation of that. Where it seems to hurt the most among bottom decile performances is when you combine surrendering yards in bulk with giving up bigger plays and allowing more touchdowns on top of that.

Actually, you can see this in terms of average yards per play right here:

AVERAGE YARDS - RANGE

AVG. WINS

AVG. LOSSES

max-6.5

3.6

8.7

6.49-6.0

4.8

7.5

5.99-5.5

5.8

6.8

5.49-5.0

8.2

4.7

4.99-4.5

8.9

4.2

4.49-min.

10.3

3.0

Here are the average records for teams either one standard deviation above or below the division mean:

AVG. WINS

AVG. LOSSES

More than 1 Std. Dev. Above Mean - Total Yards

5.5

7.2

More than 1 Std. Dev. Above Mean- Avg. Yards / Play

4.3

7.9

More than 1 Std. Dev. Above Mean - Touchdowns

4.1

8.2

More than 1 Std. Dev. Above Mean - Avg. Yards / Game

4.8

7.5

More than 1 Std. Dev. Below Mean - Total Yards

8.9

4.0

More than 1 Std. Dev. Below Mean - Avg. Yards / Play

9.7

3.5

More than 1 Std. Dev. Below Mean - Touchdowns

9.7

3.4

More than 1 Std. Dev. Below Mean - Avg. Yards / Game

9.0

4.1

More than 1 Std. Dev. Below Mean - All Metrics

9.8

3.2

More than 1 Std. Dev. Above Mean - All Metrics

3.6

8.6

So, the results are comparable to the top and bottom decile performances. In this, however, I included the averages for teams which excelled in all four categories and were above or below one standard deviation in all of them. For you edification, here are the first ten teams that qualified in this regard in both directions:

BEST

WORST

Alabama

Duke

Florida St.

Miami (OH)

BYU

Wyoming

Michigan St.

West Virginia

Florida

Toledo

Bowling Green

Idaho

Notre Dame

New Mexico St.

LSU

Eastern Mich.

Connecticut

Kansas

Rutgers

Tulane

I also looked at one or two other things as well. I sorted the table by national rank and then did a quick study of the average records of each of twelve ten-team tiers (i.e., 1-10, 11-20, etc…) and the results do indeed show a progression:

National Ranking

AVG. WINS

AVG. LOSSES

1 to 10

9.5

3.6

11 to 20

9.0

4.2

21 to 30

8.2

4.6

31 to 40

8.5

4.5

41 to 50

7.6

5.3

51 to 60

7.2

5.4

61 to 70

6.1

6.4

71 to 80

6.7

6.2

81 to 90

4.8

7.5

91 to 100

4.1

8.3

101-110

5.4

7.0

111 and below

4.8

7.4

It should be noted, for those who are not aware, that the rankings are determined by average yards surrendered per game, so you’re essentially looking at the progression for that as well. Things actually get a little intriguing, however, when you blow this up to total yards:

TOTAL YARDS

AVG. WINS

AVG. LOSSES

4000 and below

9.6

3.6

4001-4250

8.1

4.6

4251-4500

7.7

4.9

4501-4750

6.3

6.4

4751-5000

6.8

5.8

5001-5250

7.4

5.6

5251-5500

5.6

6.9

5501-5750

5.6

7.0

5751-6000

4.0

8.5

6001 and above

8.0

4.9

You will note two spikes – one at the 5001-5250 yard range, and another in the tier of teams that basically don’t believe in defense. Part of the problem in the latter group was sample size and the fact that 5 of the 6 teams in that group had WINNING records. Here is the list for each “spike”:

5001-5250

6000 and above

Georgia

Duke

Mississippi St.

West Virginia

Cincinnati

Toledo

Auburn

Louisiana Tech

Ohio

Arizona

Nebraska

Baylor

Texas A&M

Washington St.

Southern Miss.

Southern California

UAB

Army

SMU

Clemson

Northern Ill.

Oklahoma

Wake Forest

UCF

Georgia Tech

TL;DR CONCLUSION:

One of the things that I found here that actually did surprise me a little bit was just how significantly less sensitive the relative performances can be to defensive play sometimes. There are indeed teams which have the firepower on offense to outgun their opponents, and when you look at some of the teams that show up as the worst performers on defense, you see many teams that also walked away with decent records for the season as well.

Overall, you still see how much it is worth in terms of wins and losses to have a good defense. The whole idea here was to reach an approximation of that essentially using the otherwise obvious football axioms about having a good defense and what it can get you. It seems that, similar to the diary on offense, we are looking at anywhere from 1-3 wins above the mean, depending on the measure used.

Thanks for these posts. They always get me thinking. If you break out the offense and defense into rushing and passing categories does that matter? There are some who believe that the key stat in the NFL is yards per pass attempt. (see Craig Ross "The Obscene Diaries of a Michigan Fan") The team that gives up fewer and gains more per passing play seem to win a lot more in the NFL. How does the college data stack up?